We caught up with the Assassin’s Creed IV: Black Flag team in a world exclusive interview detailing the exact differences between current gen and next-gen. Many people have e-mailed us wanting to know exactly what they are, and we have delivered. Interview after the break! (Video Demo included)

WhatIfGaming:Please tell us your name and your position at Ubisoft.

The Ubisoft Team: Luc Poirier, Team Lead 3D & Alexandre Begnoche, Lead Engineer.

WhatIfGaming: What has it been like for your team releasing Black Flag IV? What was the hardest hurdle your team overcame in development?

The Ubisoft Team: Working on an AC game is always challenging and Black Flag was not the exception to the rule but overall it was a very fun experience.

I would say the 2 major technical challenges were dealing with a massive world without any transitions and having to deliver a stellar game on so many different platforms. To the usual issues and challenge that a AAA game production team has to face, a lot of unknown was added because of the PS4 and XboxOne and the short timeframe we had to work on those consoles.

WhatIfGaming: Speaking of current gen, a lot of our viewers had very specific question in regards to the “Building a Next Gen Open World ” trailer. So the things mentioned were Beaufort levels for the Sea Engine. We thought these were included with Assassin’s Creed III, are these making a return on both current gen and next gen of Black Flag IV and how has this changed in terms of the AnvilNext Engine’s newest revision for Black Flag?

The Ubisoft Team: The Beaufort levels are the mostly the same between AC3 and AC4, but now we can change them dynamically. In AC3, we would set a predetermined Beaufort level for a given naval mission, and the only way we could change it was with a camera cut. In AC4, the Beaufort level of the ocean is now dynamic: it will change depending on the mission, weather, or world position, and the transition between the different Beaufort level will be smooth.

WhatIfGaming:What are the differences with the Sea Engine between current gen and next gen? Please be specific as possible (are there different color shaders being used?) i.e. ‘Shallow Water Shaders’ as on the trailer? More sea foam? Better SSS? Higher physics simulation? More refraction in general? Note: please do not just say improved visuals on next-gen. The readers want exact details as to what is different in regards to the ocean between these two versions. Be as technical as needed.

The Ubisoft Team: The main difference for the ocean is mostly visual. The draw-distance is the major change in terms of a game of this kind with the baseline next-gen capabilities. The tessellation (amount of vertices) is four times bigger on next-gen. This help reducing drastically the aliasing and jittering that can sometime happens with high Beaufort on current gen. Regarding the lighting, only the sun (and moon) is applied on current gen. On next gen, every dynamic lights are added to the ocean lighting (i.e. explosion coming from cannon, particles). Specular computation on next gen is also different by having a more precise Fresnel (Schlick’s approximation) and as a result – this provides less aliasing.

In terms of the physics simulation, there is a 3rd frequency approximation done for waves, whereas the current-gen one only has 2 wave frequencies. Reflection is also more precise and does have more objects in it (especially particles can be part of it, like smoke coming from cannon). The visual shader is also more complex and by far the greatest change on next gen: Caustics and Rain ripples are applied, Foam uses another algorithm to be spread more elegantly (Foam churn) with higher textures, the Jackdaw’s decks get covered in water with its own reflection of the sky along with wind condition implementations, and there is volumetric fog which takes place on the oceans, which is minor but adds a nice effect. Finally a dynamic navmesh (while boarding) moves with the current of the water than remaining fixed, and also takes in water on the decks during boarding. All of these, create the most realistic virtual ocean.

In terms of land, we have god rays and 3D Foliage in our jungles. Each 3D model has a movement. We were unable to include any simplified version of this due to restraints of the open world, even though we did some things similar with 2D plants and skewing them.

WhatIfGaming: Please describe in detail how your global illumination structure works in regards to light probes. How is everything precomputed, how is radiance transfer done?

The Ubisoft Team: Our global illumination solution is based on the technique used on Far Cry 3 – Deferred Radiance Transfer Volumes. Due to differences in the game structure and different requirements we have developed a new algorithm – instead of storing precomputed radiance transfer, we stored irradiance information – in similar manner to light-mapping techniques. However, storing direct irradiance would be impossible due to dynamically changing lighting, weather and time of day, so we precomputed “normalized” information instead. Based on this information, we are able to reconstruct the final irradiance every frame in the runtime. Also both offline baking process and final memory storage used on all platforms were changed and optimized. All of those changes result in higher effect quality and more temporal and spatial resolution of indirect lighting data. We have plans to publish and present some more details on the developed global illumination technique in the future.

WhatIfGaming:In terms of Global Illumination, does the next-gen version offer more room for more environment probes. Essentially, did the team take any significant undertaking with the next generation global illumination or is it the exact same for current and next gen?

The Ubisoft Team: We investigated a better GI solution for the next gen consoles (with more probes and more data per probe), but in the end, we decided to use the same solution as the current gen console. If we had used a very different GI solution for the next gen version, it would have meant that all the data would have been duplicated and that would have been too much work to tweak two versions. The Lighting Artists team, in collaboration with the Art Director, worked very hard to create the best lighting possible for this game. For each location, they had to setup the lights for each weather type and for each hour of the day. That means a lot of permutations, and if you add the lighting for all the cut scenes, you realize that it’s a lot of data to create. That being said, there are still some differences. For example, the AO is not applied the same way.